The present invention relates to a gas turbine engine, and more particularly to a turbofan gas turbine engine having a cable driven fan variable area nozzle structure within the fan nacelle thereof.
Conventional gas turbine engines include a fan section and a core engine with the fan section having a larger outer diameter than that of the core engine. The fan section and the core engine are disposed sequentially about a longitudinal axis and are enclosed in a nacelle. An annular path of primary airflow passes through the fan section and the core engine to generate primary thrust.
Combustion gases are discharged from the core engine through a primary airflow path and are exhausted through a core exhaust nozzle. An annular fan flow path, disposed radially outwardly of the primary airflow path, passes through a radial outer portion between a fan nacelle and a core nacelle and is discharged through an annular fan exhaust nozzle defined at least partially by the fan nacelle and the core nacelle to generate fan thrust. A majority of propulsion thrust is provided by the pressurized fan air discharged through the fan exhaust nozzle, the remaining thrust provided from the combustion gases is discharged through the core exhaust nozzle.
The fan nozzles of conventional gas turbine engines have fixed geometry. The fixed geometry fan nozzles are suitable for take-off and landing conditions as well as for cruise conditions. However, the requirements for take-off and landing conditions are different from requirements for the cruise condition. Optimum performance of the engine may be achieved during different flight conditions of an aircraft by varying the fan exhaust nozzle for the specific flight regimes.
Some gas turbine engines have implemented fan variable area nozzles. The fan variable area nozzle provides a smaller fan exit nozzle diameter during cruise conditions and a larger fan exit nozzle diameter during take-off and landing conditions. The existing variable area nozzles typically utilize relatively complex mechanisms that increase engine weight to the extent that the increased fuel efficiency benefits gained from fan variable area nozzle are negated.
Accordingly, it is desirable to provide an effective, lightweight fan variable area nozzle for a gas turbine engine.